How to Contribute to ZooKeeper

This page describes the mechanics of how to contribute software to ZooKeeper. For ideas about what you might contribute, please see the ProjectSuggestions page.

Getting the source code

First of all, you need the ZooKeeper source code. Go to https://github.com/apache/zookeeper (which is a read only mirror of zookeeper git hosted on Apache) and click the fork button to create your own fork. After forking download your fork to local disk. Most development is done on the "master":

You may also want to develop against a specific release. You can list the release branches and checkout 3.4 by going into the zookeeper directory and running:

Making Changes

Before you start, send a message to the ZooKeeper developer mailing list, or file a bug report in Jira. Describe your proposed changes and check that they fit in with what others are doing and have planned for the project. Be patient, it may take folks a while to understand your requirements.

You will want to create a local branch to work under. It's convenient to name it the JIRA number:

Modify the source code and add some (very) nice features using your favorite IDE.

New unit tests should be provided to demonstrate bugs and fixes. JUnit is our test framework:

You must implement a class that extends junit.framework.TestCase and whose class name ends with Test.

Define methods within your class whose names begin with test, and call JUnit's many assert methods to verify conditions; these methods will be executed when you run ant test.

By default, do not let tests write any temporary files to /tmp. Instead, the tests should write to the location specified by the test.build.data system property.

Place your class in the src/java/test tree.

ClientTest.java is an example of a client-server test.

You can run all the unit test with the command ant test, or you can run a specific unit test with the command ant -Dtestcase=<class name without package prefix> test (for example ant -Dtestcase=ClientTest test)

Understanding Ant

ZooKeeper is built by Ant, a Java building tool. This section will eventually describe how Ant is used within ZooKeeper. To start, simply read a good Ant tutorial. The following is a good tutorial, though keep in mind that ZooKeeper isn't structured according to the ways outlined in the tutorial. Use the tutorial to get a basic understand of Ant but not to understand how Ant is used for Hadoop:

Contribute Work via Github Pull Request

We accept pull requests via github against the apache/zookeeper repository. Submitting to Apache ZooKeeper via github is no different than submitting any other pull request against a github repository. The developer needs to follow the contribution guidelines to produce changes, just like with patch files, and once it is ready, the developer produces a pull request from his/her own branch. The one constraints we have is that the title of the pull request must match the paring JIRA issue. If the JIRA issue is "ZOOKEEPER-222222: My lovely bug", then the pull request issue must also match "ZOOKEEPER-222222: My lovely bug".

We currently perform QA on pull requests, although the process is still being polished. We also have not completed the JIRA workflow when the developer submits a pull request, which means that the JIRA does not transition to Patch Available when a pull request is submitted. We are currently discussing on the list how to adapt our workflow.

Example workflow

there are many ways to setup your git environment but this one example:

fork the apache github repo

make a local clone of your fork

add the apache github repo

make sure you are uptodate

create a branch named after the issue you are working on

<jiraNumber> is the JIRA you will be working on.

make your changes

sorry can't help you here. it's all up to you to fix the bug

commit everything

do you will want to do some combination of git add and git commit to get all your changes committed. when you run git commit, you only need a single line in the commit message it should have the form ZOOKEEPER-jiraNumber: jiraTitle.

push your change to git hub

generate a pull request

go to the github page that lists your branches. you will see a pull request button that you can press. Please make sure your pull request description captures enough information so reviewers can get an idea of what the pull request is targeting without digging into the JIRA or looking into the code. When the pull request is merged, the description will be part of the commit message. Here is an example of a descriptive pull request looks like: https://github.com/apache/zookeeper/pull/211

Check List for Pull Request

This is a check list of things we'd like a contributor to do before opening a pull request.

Unit Tests

Before submitting your pull request, you are encouraged to run the same tools that the automated Jenkins CI system will run on your patch. This enables you to fix problems with your pull request before you submit it. The test Ant target will run your patch through the same checks that Jenkins currently does.

To use this target, you must run it from a clean workspace (ie git status shows no modifications or additions). From your clean workspace, run:

At the end, you should get a message on your console that indicates success.

Some things to note:

you may need to explicitly set ANT_HOME. Running ant -diagnostics will tell you the default value on your system.

you may need to explicitly set JAVA_HOME.

Please make sure that all unit tests succeed before submitting pull request and that no new javac compiler warnings are introduced by your pull request

After a while, if you see

all is ok, but if you see

then please examine error messages in build/test and fix things before proceeding.

Javadoc

Please also check the javadoc.

Examine all public classes you've changed to see that documentation is complete, informative, and properly formatted. Your patch must not generate any javadoc warnings.

Documentation

The source documentation is available in src/docs directory. It can be regenerated using forrest (as documented here) however the contributor is not responsible for submitting this as part of the pull request. To be clear: the pull request should include changes to src/docs but not the toplevel (of the source tree) docs directory.

Please don't do in pull request:

reformat code unrelated to the bug being fixed: formatting changes should be separate patches/commits.

comment out code that is now obsolete: just remove it.

insert comments around each change, marking the change: folks can use subversion to figure out what's changed and by whom.

make things public which are not required by end users.

Please do in pull request:

try to adhere to the coding style of files you edit;

comment code whose function or rationale is not obvious;

Final Checks on Pull Request

Please note that the attachment should be granted license to ASF for inclusion in ASF works (as per the Apache License §5).

Folks should run ant clean test javadoc before submitting pull request. Tests should all pass. Javadoc should report no warnings or errors. Jenkin's tests are meant to double-check things, and not be used as a primary patch tester, which would create too much noise on the mailing list and in Jira. Submitting patches that fail Jenkins testing is frowned on, (unless the failure is not actually due to the patch).

If your PR involves performance optimizations, they should be validated by benchmarks that demonstrate an improvement.

If your PR creates an incompatibility with the latest major release, then you must set the Incompatible change flag on the issue's Jira 'and' fill in the Release Note field with an explanation of the impact of the incompatibility and the necessary steps users must take.

If your PR implements a major feature or improvement, then you must fill in the Release Note field on the issue's Jira with an explanation of the feature that will be comprehensible by the end user.

Code Review and Accept Pull Request

Once a "+1" comment is received from the automated patch testing system and a code reviewer has set the Reviewed flag on the issue's Jira, a committer should then evaluate it within a few days and either: commit it; or reject it with an explanation.

Please be patient. Committers are busy people too. If no one responds to your patch after a few days, please make friendly reminders. Please incorporate other's suggestions into your patch if you think they're reasonable. Finally, remember that even a patch that is not committed is useful to the community.

Should your patch receive a "-1" from the Jenkins testing, select the Resume Progress on the issue's Jira, update pull request with necessary fixes.

Committers: for non-trivial changes, it is best to get another committer to review your pull request before commit. Please also try to frequently review things in the patch queue.

Committing Guidelines for committers

Apply the patch uploaded by the user. Edit the CHANGES.txt file, adding a description of the change, including the bug number it fixes. Add it to the appropriate section - BUGFIXES, IMPROVEMENTS, NEW FEATURES. Please follow the format in CHANGES.txt file. While adding an entry please add it to the end of a section. Use the same entry for the git commit message.

Jira Guidelines

Please comment on issues in Jira, making their concerns known. Please also vote for issues that are a high priority for you.

Please refrain from editing descriptions and comments if possible, as edits spam the mailing list and clutter Jira's "All" display, which is otherwise very useful. Instead, preview descriptions and comments using the preview button (on the right) before posting them. Keep descriptions brief and save more elaborate proposals for comments, since descriptions are included in Jira's automatically sent messages. If you change your mind, note this in a new comment, rather than editing an older comment. The issue should preserve this history of the discussion.

Stay involved

Contributors should join the ZooKeeper mailing lists. In particular, the commit list (to see changes as they are made), the dev list (to join discussions of changes) and the user list (to help others).